audit(#622): sweep hardcoded colors + add checkColorLiterals guard (#626)

Removed docs/color-hardcoded-audit.md per request. Replaced 2 hardcoded
Color literals with theme tokens; added CI guard blocking new literals.

Co-authored-by: Hy4ri <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/ui/sessions/SessionsScreen.kt

@@ -806,7 +806,7 @@ fun SessionsScreen(
                                 CircularProgressIndicator(
                                     modifier = Modifier.size(18.dp),
                                     strokeWidth = 2.dp,
-                                    color = Color.White,
+                                    color = statusColors.onError,
                                 )
                             } else {
                                 Icon(